The overall objective of this research is the development of new methods for the study of the structure and dynamics of biological membranes and the application of these methods to the study of lipid- lipid and lipid-protein interactions. Specifically, we will extend the use of Raman spectroscopy and modern methods of normal mode and conformational calculation to study the chain isomerization events in the solid-like to liquid-like phase transition of model membranes and the use of electronic spectral methods (fluorescence, absorption, CD and energy transfer) to study lipid fluidity and polarizability, lipid phase separations and lipid protein interactions. The major novel feature of this work is the use of linear conjugated polyene fatty acids and polyene labeled lecithins as fluorescence, energy transfer and resonance Raman probes of membrane structure. These fluorescent molecules are nearly identical to normal membrane components in terms of molecular dimensions and shape. The fluorescence of these compounds has been found to be a sensitive function of their environments. They accept energy from fluorescent aromatic amino acids and show a strong induced circular dichroism on binding to proteins. Biological incorporation of these polyenes into membranes has been demonstrated.